1. Field of the Invention
This invention relates to a hinge joint for the access door of a videocassette of the type used in a video recording and playback machine and, more particularly, a hinge joint for the door of a "U-Matic" cassette developed by Sony Corporation.
2. Description of the Prior Art
As is best seen in FIG. 2 of U.S. Pat. No. 3,809,219, a prior art video tape cassette or videocassette 10 typically comprises a length of magnetizable recording tape 19, two reels 17 and 18 each supporting a different helically-wound end portion of the length of tape 19, and a generally rectangular housing 11 enclosing and supporting the reels 17 and 18 for rotation to transfer tape 19 between the reels 17 and 18. The housing 11 includes an outer front wall having generally planar end portions and a recessed portion 16 defining a tape access area along the outer surface of the housing 11, and guide pins 20 and 21 for guiding tape between the reels 17 and 18 through the outer wall and across the recessed portion 16 to afford access thereto by the mechanism 62 of a video tape recording/playback machine. A door 22 is pivotally mounted on the housing 11 by a hinge assembly 23, 24 for movement between a closed position over the length of tape 19a extending through the tape access area (FIG. 5) and an open position (FIG. 1) spaced from the tape access area 16, with the door 22 being biased to its closed position by a helically-wound spring 25 tensioned between the housing 11 and the door 22.
While the use of such a spring 25 is effective in biasing the door 22 to its closed position, it is difficult to assemble to the cassette 10 and thus adds to the cost of the cassette 10.
U.S. Pat. No. 4,130,221 is an improvement over the prior cassette described above in that the helically-wound spring is eliminated and replaced by a torsion spring which operates as a hinge pin in addition to biasing the cassette door to its closed position. The cassette 50 of U.S. Pat. No. 4,130,221 includes a metal door 54 which has two rolled, cylindrical projections 74 which mate with a rolled, cylindrical projection 76 of a hinge plate 70 to form the knuckle joint of a hinge for the door 54. The torsion spring 52 passes through the rolled portions 74 and 76 of the door 54 and 70, respectively, to provide a hinge pin and includes end portions 80 and 82 attached to the door 54 and the hinge plate 70, respectively, which operate to bias the door 54 into its closed position.
The torsion spring of U.S. Pat. No. 4,130,221 is effective to simplify the biasing mechanism for the door 54, but the metal door 54, and particularly its rolled, knuckle joint portions 74, is difficult to fabricate and attachment of the hinge plate 70 to the cassette 50 requires assembly time and thus adds to the cost of the cassette 50.